In recent years, awareness in terms of the need to control global warming has been rising, and in particular, hydrogen fuel automobiles using hydrogen as fuel, such as fuel cell electric automobiles and hydrogen engine automobiles, have been actively developed for the purpose of reducing carbon dioxide discharged from vehicles. A hydrogen tank which is filled with hydrogen gas is mounted as a hydrogen supply source in general hydrogen fuel automobiles.
In methods for storing and transporting hydrogen, use of metals referred to as “hydrogen storage alloys” which store hydrogen so as to become hydride under certain temperature and pressure conditions and release hydrogen under different temperature and pressure conditions when necessary, has been drawing attention. Hydrogen tanks using a hydrogen storage alloy can store more hydrogen than a tank with the same volume, and therefore, have been drawing attention.
Hydrogen tanks are filled with hydrogen gas at installations referred to as hydrogen stations, which correspond to gas stations and LP gas stations. Hydrogen stations are provided with, for example, hydrogen multi-cylinder frames containing a number of cylinders and dispensers for filling the hydrogen tank of vehicles with hydrogen supplied from the hydrogen multi-cylinder frame. In addition, the hydrogen tank is filled with hydrogen gas using the difference in pressure between the hydrogen multi-cylinder frame and the hydrogen tank in such a state that a coupler provided at the end of the hose of the dispenser is linked to the opening for filling the above described hydrogen tank.
While the hydrogen tank is being filled with hydrogen gas, the temperature inside the hydrogen tank becomes high, and therefore, it takes time to fill the hydrogen tank with hydrogen gas, unless the hydrogen tank is filled with hydrogen gas while being cooled. In addition, in the case where the amount of hydrogen with which the hydrogen tank is filled is increased by making a hydrogen storage alloy store hydrogen, the hydrogen storage reaction in the hydrogen storage alloy is an exothermal reaction, and therefore, the hydrogen storage reaction does not progress smoothly, unless the hydrogen tank is cooled.
It is possible for fuel cell automobiles with a hydrogen tank having a hydrogen storage alloy inside to have such a system that a heat medium after cooling the fuel cell is used as the heat medium for heating the hydrogen storage alloy when hydrogen is released from the hydrogen storage alloy, and the same heat medium is used as the heat medium for cooling the hydrogen storage alloy when the hydrogen storage alloy stores hydrogen. In this system, the heat medium is cooled by a radiator which is mounted in the fuel cell automobile. In addition, when the fuel cell operates, the hydrogen storage alloy is heated by the heat medium after cooling the fuel cell, so that hydrogen is released smoothly, and when the hydrogen tank is being filled with hydrogen, the fuel cell stops operating, and the heat medium cooled by the radiator is used for cooling the hydrogen storage alloy instead of for cooling the fuel cell. In this case, when the fuel cell operates, the fuel cell is cooled and the hydrogen storage alloy is heated smoothly by the heat medium.
However, in the case where the hydrogen storage alloy stores hydrogen, that is to say, when the hydrogen tank is being filled with a large amount (for example, 5 kg) of hydrogen in a short period of time (for example, within 5 minutes) under high pressure (for example, 35 MPa), general radiators and fans for automobile use lack the ability to release heat generated in the hydrogen storage alloy and heat resulting from gas compression to the outside.
The ratio of hydrogen fuel automobiles equipped with an air-conditioning apparatus or an air-cooling apparatus is high, as is that of automobiles having an internal combustion engine. Japanese Laid-Open Patent Publication No. 7-186711 discloses a hydrogen fuel automobile having an air cooling apparatus having a condenser for condensing a compressed refrigerant gas and an evaporator for evaporating an expanded refrigerant liquid, and a heat exchanging apparatus which is provided inside the tank having a hydrogen storage alloy inside and forms a portion of a heated refrigerant passage. The above described heat exchanging apparatus has a first heat exchanger provided inside the tank having a hydrogen storage alloy inside and a second heat exchanger provided in at least either the passage for air cooled by the above described air cooling apparatus or the passage for cooling air that cools the condenser of the air cooling apparatus. This hydrogen fuel automobile is provided with a heat exchanging apparatus separately from the air cooling apparatus, and cold energy in the hydrogen storage alloy accompanying the release of hydrogen from the hydrogen storage alloy is conveyed to the refrigerant of the heat exchanging apparatus through the first heat exchanger, and cold energy that is conveyed to this refrigerant is conveyed to the air in the air cooling apparatus or air for cooling the condenser in the air cooling apparatus through the second heat exchanger. That is to say, the cold energy of the hydrogen storage alloy is used to reduce energy consumption in the air cooling apparatus.
In addition, Japanese Laid-Open Patent Publication No. 2000-88196 discloses a hydrogen storage alloy system mounted in an automobile, which is provided with a heat medium circulation system, a cooling portion for cooling the heat medium, and a heating portion for heating the heat medium. The heat medium circulation system allows a heat medium to circulate through the hydrogen storage alloy mounted in the vehicle, so that heat is exchanged between the heat medium and the above described hydrogen storage alloy. This hydrogen storage alloy system mounted in an automobile selectively makes the above described cooling portion and the above described heating portion operate when the above described hydrogen storage alloy is being filled with hydrogen or when hydrogen is released from the above described hydrogen storage alloy, respectively.
In the case where the hydrogen tank is filled with hydrogen at an outdoor temperature of 30° C. in such a state that a radiator and a fan mounted in a general automobile (for example with an amount of flow of cooling water: 60 L/min, wind velocity: maximum 2 m/sec) are operating, the hydrogen tank can be filled to only approximately 85% (4.25 kg) of the amount of hydrogen with which the tank is filled when full, after five minutes have elapsed starting from a state where the hydrogen tank is empty. In order for the hydrogen tank to be filled with hydrogen to an amount of 95% (4.75 kg) or more of hydrogen with which the tank is filled to the fullest in five minutes, it is necessary for the wind velocity from the fan to be no less than 6 m/sec. In the case where a fan which can provide this wind velocity is mounted in a fuel cell automobile, however, a large space for installation becomes necessary, and the fuel cell automobile ends up being equipped with a fan of which the performance is excessive at all times except when the tank is being filled with hydrogen.
Japanese Laid-Open Patent Publication No. 7-186711 describes use of cold energy from the hydrogen storage alloy accompanying release of hydrogen from the hydrogen storage alloy inside a tank having a hydrogen storage alloy inside for cooling air in the air cooling apparatus or cooling air that cools the condenser in the air cooling apparatus. Japanese Laid-Open Patent Publication No. 7-186711, however, does not have any description in terms of the tank having a hydrogen storage alloy inside being filled with hydrogen in a short period of time.
Japanese Laid-Open Patent Publication No. 2000-88196 has as an objective to make it possible to fill a hydrogen storage alloy with hydrogen in such a state that the hydrogen storage alloy is mounted in a vehicle (in an on-board state). Japanese Laid-Open Patent Publication No. 2000-88196, however, does not have any description concerning the objective of the present invention to fill a hydrogen tank with hydrogen in a short period of time in comparison with a case where the hydrogen tank is cooled using the radiator and the fan mounted in the automobile.